Question

An online clothing retailer monitors its order-filling process. Each week, the quality control manager selects a random sample of size n = 350 orders that have been filled but have not shipped. The contents of the shipping container are checked against the items ordered by the customer (including color and size categories), and the order is categorized as defective or non-defective. A p chart is used to identify whether or not the process is in control.

The graph below shows the proportion of defective orders for 20 consecutive weeks of samples.

3.4% of orders are incorrectly filled when the process is in control; treating the data from the 20 samples as one large sample, the proportion of defective items is 0.018.

Using the standard error of the sample proportion (rounded to 3 decimal places), calculate the center line, lower control limit, and upper control limit and add them to the control chart.(how to calculate)

The quality control engineer uses the p chart to identify whether or not the order-filling process is in a state of control. She concludes that the process is________________ because______________________________________________ .

Instead of a p chart, suppose that the online clothing retailer uses a np chart to identify whether or not the process is in a state of control.

The quality control engineer would draw the center line at________________ , the UCL at______________ , and the LCL at_______________ ; she would conclude that the order-filling process is__________________ .

Answer 1